cd build
make
cd -
qemu-system-riscv32 -nographic -machine virt -net none \
        -chardev stdio,id=con,mux=on -serial chardev:con \
        -mon chardev=con,mode=readline -bios none \
        -smp 1 -kernel ./bin/rv.elf 
#-s -S开启gdb调试

